This invention relates to resid hydrotreating and, more particularly, to a feed distributor and process for feeding oil and gas to a reactor.
In the past, spiraling oil costs, extensive price fluctuations, and artificial output limitations by the cartel of oil producing countries (OPEC) have created instability and uncertainty for net oil consuming countries, such as the United States, to attain adequate supplies of high-quality, low-sulfur, petroleum crude oil (sweet crude) from Saudi Arabia, Nigeria, Norway, and other countries at reasonable prices for conversion into gasoline, fuel oil, and petrochemical feedstocks. In an effort to stabilize the supply and availability of crude oil at reasonable prices, Amoco Oil Company has developed, constructed, and commercialized extensive, multimillion dollar refinery projects under the Second Crude Replacement Program (CRP II) to process poorer quality, high-sulfur, petroleum crude oil (sour crude) and demetalate, desulfurize, and hydrocrack resid to produce high-value products, such as gasoline, distillates, catalytic cracker feed, metallurgical coke, and petrochemical feedstocks. The Crude Replacement Program is of great benefit to the oil-consuming nations by providing for the availability of adequate supplies of gasoline and other petroleum products at reasonable prices while protecting the downstream operations of refining companies.
During resid hydrotreating, resid oil (resid) is upgraded with hydrogen and a hydrotreating catalyst in a three-phase mixture of oil, catalyst, and gas bubbles to produce more valuable lower-boiling liquid products. In conventional, prior art resid hydrotreating units, resid oil (resid) and hydrogen are fed and distributed in the reactor along one side of the reactor or from opposite sides of the reactor and are not adequately mixed. This causes an imbalance of liquids (oil) and gases and poor distribution of oil in the grid comprising the bubble tray and bubble caps. Poorly mixed feeds decrease the effectiveness of hydrotreating and diminish the conversion of resid to more valuable lower-boiling liquid products.
Poorly mixed feeds of resid and hydrogen-rich gases can cause hot spots, stagnant zones, excess gas channeling, and loss of product quality. It will also cause the oil (resid) to advance (rise) further up one side of the reactor than the other and increase the maldistribution of the oil and gas feeds.
Nonuniform mixtures of resid and hydrogen-rich gases can accelerate coke formation, increase solids buildup, and plug up the grid. It can lead to premature shutdown, extended downtime, and increased frequency of maintenance and repair. Increased maintenance and repair requires additional manpower and is time consuming, tedious, and expensive. It also decreases the reactor's efficiency and adversely affects the profitability of the unit.
While various aeration diffusers have been used in sewage treatment plants, such as those shown in U.S. Pat. Nos. 3,220,706; 3,424,443; 3,608,834; and 3,954,922; such diffusers have not been used in reactors in oil refineries nor do they appear capable of mixing and distributing gases and oils, such as resid.
It is, therefore, desirable to provide an improved feed distributor and process which overcome most, if not all, of the preceding problems.